清洗工艺对GH4099蜂窝夹层结构钎焊性能的影响

目的 研究激光清洗和离子轰击对GH4099蜂窝夹层结构钎焊性能的影响,优化GH4099蜂窝夹层结构焊前清洗工艺。方法 分别用400#砂纸、不同激光功率(60~200 W)、不同离子轰击时间(1~2 h)对GH4099带材表面进行了砂纸打磨、激光清洗和离子轰击试验,分析了激光清洗和离子轰击对GH4099表面形貌、O元素含量、BNi2钎料润湿性的影响,测试了不同清洗工艺下蜂窝夹层结构钎焊接头的拉伸性能。结果 随激光功率从60 W增加到100 W,GH4099表面O含量逐渐降低,表面粗糙度逐渐增大,钎料润湿面积百分比增加到83.5%,润湿性增加。当激光功率大于100 W时,表面残留网状分布的氧化物,导致钎料润湿性降低。当激光功率进一步增加到200 W时,氧化物网状分布现象减轻,润湿性随之增加,粗糙度也有所降低;随离子轰击时间从1 h增加到2 h时,带材表面氧化皮逐渐去除干净,钎料润湿性随之增加,钎料对离子轰击2 h的表面的润湿面积百分比达到91.2%,与400#砂纸打磨的相当。经离子轰击2 h、1 020 ℃-15 min钎焊获得的夹层结构等效抗拉强度为11.9 MPa。结论 与激光清洗相比,离子轰击可以同时去除蜂窝型面及附近侧壁部分的氧化皮,能更有效地改善钎料对蜂窝基体的润湿性。     

Study of ion bombardment of SiC ceramics: Surface and interfacial reaction modification

Ar ion bombardment was conducted to modify the SiC surface microstructures, which had a vital effect on the interfacial microstructure and shear property of brazing joints. The amorphous layer with thickness of ∼120 nm was formed on the bombarded surface, accompanied with plenty of dislocations and twins beneath the amorphous layer. Reliable SiC/AgCu-Ti/SiC joints were brazed in vacuum at 900 °C for 10 min, and the interfacial microstructure was investigated by SEM, EDS and TEM in detail. When the ion bombarded SiC was used as substrates, the microstructure of brazing beam was optimized as SiC / Ti₅Si₃ + TiC mixed layer / Ag(s,s) + Cu(s,s) containing TiCu / Ti₅Si₃ + TiC mixed layer / SiC, in which the interfacial stratification was eliminated compared to the conventional SiC brazing. The shear strength was improved to 30.9 MPa with ion bombardment, which was ∼72.6 % higher than that of the original SiC joints without ion bombardment. The proposed Ar ion bombardment method provides a novel way to modify the brazability of ceramics.     

Effects of substrate bias voltage on adhesion of DC magnetron-sputtered copper films on E24 carbon steel: investigations by Auger electron spectroscopy

The adhesion strength of copper thin films on E24 carbon steel substrates was studied using the scratch test via the critical load. Coatings were deposited by a DC magnetron sputtering system. All substrates were mechanically polished; some of them were directly coated and others were ion-etched by argon ions prior to deposition process. The effects of substrate negative bias voltage during the film growth were investigated. Experimental results showed that the critical load depended on the bias voltage and that the higher bias voltage, the better adhesion. It was also observed that the deposition rate of deposited films gradually decreased with the increase of the substrate bias voltage. Furthermore, the working pressure during the substrate ion bombardment etching greatly affected the critical load. Scanning electron microscopy was used to observe the scratch tracks to accurately evaluate the critical load. Substrate surface profiles obtained by a mechanical profilometer showed that the critical load increased with the increase of the surface roughness. The analysis by Auger electron spectroscopy revealed that the interface, in case of an unbiased substrate, was relatively narrow and abrupt. However, in case of a bias voltage application, the interface was wider and more diffuse. These results suggest that the mechanisms involved in critical load enhancement are due firstly to the substrate surface roughness and the substrate temperature generated by the ion bombardment, secondly to the physical mixing in the interfacial domain and the densification of the deposited material created by the bias voltage.     

Synthesis and XPS investigation of superdense lithium-graphite intercalation compound, LiC2

The superdense lithium-graphite intercalation compound (GIC),LiC₂, first synthesized by the author was prepared by the original technique in a piston-cylinder high-pressure chamber with internal heater. Cleaved surfaces of this compound, LiC₃, LiC₆ and pristine graphite were studied by the X-ray photoelectron spectroscopy (XPS) technique. It was shown that chemical shifts of carbon do not vary in the range LiC₆ to LiC₂ which suggests that the additional lithium intercalation into LiC₆ gives no significant change in the charge transfer rate per carbon atom. Carbon/lithium atom ratios were obtained for freshly cleaved surfaces and for the surfaces after argon ion bombardment. It was shown that the bombardment results in the surface decomposition of LiC₂-GIC.     

Ionic bombardment of stainless steel by nitrogen and nickel ions immersion

A new nitriding process was used to carry out the ionic bombardment, in which nickel ion was introduced. The microstructure, composition and properties of the treated stainless steel were studied by means of scanning electron microscopy（SEM）, micro-hardness test and electrochemistry method. The results show that the hardness of the stainless steel is greatly increased after ionic bombardment under nitrogen and nickel ions immersion. Vickers＇ hardness as high as Hv1268 is obtained. The bombarded stainless steel is of a little reduction in corrosion resistance, as compared with the original stainless steel. However, as compared with the traditional ion-nitriding stainless steel, the corrosion resistance is greatly improved.     

哌嗪乙氧基雌酮的电子电离质谱和快原子轰击电离(－)质谱测定及裂解途径

哌嗪乙氧基雌酮是一种可望用于防治骨质疏松症的全新合成的雌激素类化合物，本文采用EI-MS、FAB (－) -MS 、ESI-MS三种质谱技术分别对其结构和裂解途径进行了研究。采用FAB(－) -MS，获得m/z 404［M+Na-H］^-、382［M］^-、381［M-H］^-质谱峰；采用EI-MS, 获得m/z 382 M^+•；采用ESI-MS, 获得m/z 383［M+H］⁺。分子离子m/z 382 M^+•和主要特征子离子与其结构特征相符，并解释了其中的主要特征子离子，对其结构和裂解途径进行了确证。     

一种电子枪分析设计

设计一种大功率轰击型六硼化镧电子枪。以传热学理论基础和重要结论为依据,得出能减小阴极电子枪热量损失的几个设计与材料选取原则。利用有限元法对轰击型六硼化镧电子枪阴极模型进行热模拟。依据模拟结果设计一种轰击型六硼化镧阴极电子枪,其发射面直径为2.0 mm,当加热功率为80.0 W时,阴极温度达到1 569℃所发射电子束束流密度达到5.55 A/cm2,并且发射稳定、束斑均匀、发散度小,反复暴露于大气后仍能正常工作。     

大功率半导体激光器的腔面钝化

大功率半导体激光器的腔面退化是影响其寿命和可靠性的重要因素,长期以来一直是人们关注和研究的重点。本文利用离子铣结合腔面钝化还原层的方法对大功率半导体激光器的腔面进行处理。结果显示,离子铣腔面钝化能够在一定程度上减少半导体激光器的功率退化,168h加速老化后退化幅度降低4.5%;同时该技术对老化过程中COD阈值降低有明显的抑制作用,可有效减少使用中的突然失效。结果表明,该技术能够改善半导体激光器的腔面特性,器件的可靠性和使用寿命可望得到提高。     

Relation between the plasma characteristics and physical properties of functional zinc oxide thin film prepared by radio frequency magnetron sputtering process

The ZnO thin film was deposited on a glass substrate by a RF reactive magnetron sputtering method. Results showed that plasma density, electron temperature, deposition rate and estimated ion bombardment energy increase with increasing applied RF power. Three distinct power regimes were observed, which are strongly correlated with plasma properties. In the low-power regime, the largest grain size was observed due to slow deposition rate. In the medium-power regime, the smallest grain size was found, which is attributed to insufficient time for the adatoms to migrate on substrate surface. In the high-power regime, relatively larger grain size was found due to very large ion bombardment energy which enhances the thermal migration of adatoms. Regardless of pure ZnO thin film or ZnO on glass, high transmittance (> 80%) in the visible region can be generally observed. However, the film thickness plays a more important role for controlling optical properties, especially in the UV region, than the applied RF power. In general, with properly coated ZnO thin film, we can obtain a glass substrate which is highly transparent in the visible region, is of good anti-UV characteristics, and is highly hydrophobic, which is highly suitable for applications in the glass industry.     

籼型杂交水稻保持系IR58025B pin2转基因植株

杂交水稻技术在中国及其他国家已作为发展水稻生产,满足不断增加的人口对粮食需要的一条关键途径．而另一方面,据估计因螟虫危害造成水稻年均损失为5％～10％,有时高达60％～95％．应用马铃薯蛋白酶抑制剂基因(potato proteinase inhibitor Ⅱor pin2)进行粳稻的遗传转化实验表明,其转基因粳稻植株对螟虫的抗性显著提高,且该转基因能在后代中稳定遗传(Duan et al．,1996)．为了改良杂交水稻对螟虫的抗性,以大面积应用的籼型杂交稻保持系IR58025B成熟胚为外植体材料、以pin为目的基因、通过基因枪法高效获得了大量转基因植株．PCR检测结果表明转基因pin2成功地整合于植株基因组中．三化螟幼虫饲喂试验结果初步证实了该转基因在转基因当代植株中的表达．